A fertility curse/blessing plagues a family, making it so that anybody who gets close to them with good enough genetics is 'marked' by their curse/blessing. This amplifies their pheromone output, fertility/virility, and overall physique until they are blessed with a body meant for mass procreation, with the blessing only getting worse the more offspring they make.
One day, one of the family daughters brings home a tgirl from school, who suddenly experiences both sides of the curse, making her both feminine and masculine at the same time, leading to her going on a breeding rampage that sees more and more women drawn to her, with each pregnancy drawing more to her like moths to a flame~.
It did seem more like a blessing in disguise than a curse, especially for the cute t girl who was dating one of the daughters in college, and was therefore marked with the blessing, that started really amplifying her body's attributes, in the best way possible.
Her figure became more feminine, with tits and ass experiencing most of the growth, becoming more and more curvaceous, she also became more toned and powerful, packing rock solid abs to contrast with her soft, beautiful breasts that were overflowing all of her clothes already.
Meanwhile, her cock and balls were expanding at an insane rate too, doubling and then tripling in size from what they were before, radiating powerful pheromones that would attract a lot of 'mates', the first one, of course, being the girl she was dating, the one who marked her in the first place. The trans girl happily pinned her down and bred her right on the spot, after feeling the first surge of growth, though she was far from done. Obviously, the now pregnant, extremely aroused girlfriend would know that this was also far from the ending, as she had seen what had happened to others who had experienced the curse in the past, and so she wasn't surprised when the trans girl went in public, showing off her body, and attracting multiple women to get closer to her, before breeding them one by one, her cock and balls causing her horny levels to break through any possible human ceiling, beyond what anyone else could even imagine, all thanks to her growing body and her need to breed as many lovely ladies as possible.
The breeding rampage would go on throughout the entire city, and almost all women who locked eyes with the ever swelling, hyper hung cutie would be drawn to her in seconds, feeling their ovaries 'explode', hyperovulating to become as pregnant as possible for this virile babe~
Her marked body was spreading its seed everywhere, and her now altered genes were going to get passed on by so, so many, that she might have caused this 'curse' to become a much larger scale blessing, bringing forth a fertile, hyper breeding society for the next generations.














